Infrared surface heating unit with two filaments



March 26, 1968 R- s. GAUGLER ETAL 3,375,346

INFRARED SURFACE HEATING UNIT WITH TWO FILAMENTS Filed Sept. 22, 1965 INVENTORS Gaug/er 80 mm 2 W M m w F Mmmd mww a 8 0 3 5 M m 2 2 lr ll- L l w VI N I I I I l I l I I ll L 4 a 52 2 e m 5 2 \L I I in 6 w 7 6 7 M W 8 8 4 6o 72 Their Afforney United States Patent Oh 3,375,346 Patented Mar. 26, 1968 Flee ABSTRACT OF THE DISCLOSURE In preferred form an infrared surface heating unit including an upper non-opaque utensil supporting plate and a lower infrared reflector plate enveloping a first resistance element and an energization circuit for pulsatingly energizing the first resistance element into a visible light range observable through the utensil supporting plate, a

second smaller wattage resistance element and a second energization circuit for continuously energizing the second resistance element to continuously illuminate the upper support plate.

This invention relates to infrared surface heating units and more particularly of the type including high temperature electrical resistance elements energizable into a temperature range for producing noticeable, visible light emissions from the resistance elements.

In order to improve electrical surface heating units for use in electrical ranges or the like, it has been proposed to utilize an unsheathed high energy electrical resistance element that is energizable to be electrically self-heated into an infrared radiant temperature range. In these cases, the energy output from the resistance element primarily heats utensils supported on the surface unit through direct radiation rather than conductive heating. One such structure is illustrated in US. Patent No. 2,859,368, issued Nov. 4, 1958, to Biggs et al.

In such structures, it is desirable to obtain a variable heat output from the surface unit as, for example, by utilizing a thermostatic switch of the pulsing energy type. In such cases it has been found that the high temperature of the self-heated resistance elements causes a very noticeable amount of visible light to be directed outwardly from the surface heating unit and because of the provision of an energy pulsing means to vary the heat output of the surface heating unit, the visible light occurs as noticeable pulsations that are extremely distracting.

Accordingly, an object of the present invention is to improve infrared surface heating units of the type having resistance elements that are pulsatingly energized by selfheating into and out of the visible light range by the provision of a secondary lower wattage resistance element in the unit and associated switch means for continuously energizing the secondary resistance element to produce a background of illumination that damps out undesirable pulsations of visible light from a primary resistance element in the heater.

A further object of the present invention is to improve infrared surface heating units of the type including an upper utensil supporting plate of infrared transmissive material and a lower reflective surface located in spaced relationship with the utensil supporting plate and wherein a resistance element is included between the plate and surface that is pulsatingly energized into and out of the visible light range by the provision of a secondary lower wattage electrical resistance element that is disposed with respect to the upper plate and the reflective surface to produce a constant background of illumination directed through the upper plate by the reflective surface to damp out pulsing light from the primary resistance element throughout substantially the full planar extent of the upper plate.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown,

In the drawings:

FIGURE 1 is a view in perspective of an electrical range including the surface heating unit of the present invention; and

FIGURE 2 is an enlarged view in vertical section taken along the line 2'-2 of FIGURE 1 including a diagrammatically shown associated electrical circuit.

Referring now to the drawing, in FIGURE 1 an electrical range 10 is shown including an upper surface 12 having a plurality of openings 14 therethrough. Each of the openings 14 has a surface heating unit 16 therein constructed in accordance with the present invention. Eachof the surface heating units 16 has the heat output thereof varied by switch means including a manually rotatable control member or knob 17 located on a representatively shown rear control panel 20 of the range 10.

In FIGURE 2, one of the improved surface heating units 16 is illustrated as including anupper utensil supporting plate 18 of a suitable infrared transmissive material that overlies the opening 14 through the top 12. The plate 18 includes a downwardly depending peripheral flange 20 thereon that supportingly engages the upper surface of the top 12 around the opening 14. The unit 16 further includes a support member 22 having an upper end portion 24 which overlies and is supportingly engaged by the top 12 at the opening 14 therein. A depending portion 26 of the member 22 has a lower inwardly turned segment 28 on which is supported an electrically insulated base 30 of an evacuated glass bulb 32 of infrared transmissive material including a top 34 located in close spaced relationship with the utensil supporting plate 18 at a point therebelow. The bulb 32 further includes a skirt 36 that is inclined inwardly and downwardly of the top 34 to merge with a sealed neck 38 of the bulb 32 which is located in the electrically insulated base 30.

A high Wattage electrical resistance element or filament 40 is located within the bulb 32. The filament 40 is shown schematically in the bulb 32 but it will be appreciated by those skilled in the art that suitable ceramic electrical insulating pedestals can be provided to locate the resistance element 40 at a predetermined point within the bulb 32 whereby infrared emissions therefrom will be focused with respect to an infrared reflective surface 42 formed on the skirt 36 and the neck 38 of the bulb 32.

Additionally, a lower wattage electrical resistance element or filament 44 is located within the bulb 32 and supported therein in a manner like filament 40.

In the illustrated arrangement, the filament 40 is electrically connected across a suitable power source shown as including wires L and L of a 220-volt power source. More particularly, the energization circuit for the filament 40 includes a conductor 46 from wire L which is electrically connected to an electrical selector switch assembly .or controller 40 which is operated by positioning the control knob 18. When the control knob 18 is moved from an off position, it closes a line switch 50 to connect the conductor 46 to a conductor 52 which is electrically connected to a terminal 54 in the insulated base 30 of the unit 16. A lead wire 56 from terminal 54 is connected to one side of the filament 40. The opposite side of the filament 40 is connected to a lead wire 58 that is connected to a terminal 60 in turn connected to conductor 62 back to the switch assembly 48.

In order to obtain a variable heat output from the filament 40, the energization circuit has the conductor 62 electrically connected to a heater 64 which is electrically connected to a polymetallic thermally responsive element 66 having a fixed end and a movable end on which is carried a contact 68 which is selectively positioned by thermal deflection of the element 66 into and out of electrical engagement with a contact 70, The contact 70 is connected by a conductor 72 to another line switch'74 opened and closed by the positioning of the control knob 18 to complete the energization circuit through a conductor 76 back to the wireL Adjusting cam means 77 or the like adjusts the relationship between contacts 68, 70 to vary the rate of opening and closing thereof as produced by deflection of element 66'whereby a pulsing energy control is achieved.

In addition to the energization circuit for the filament "40, the switch 48 completes an energization circuit for the second resistance element 44 from wire L through conductor 46, the line switch 50, conductor 52,'terminal S4 and lead wire 56 to one side of the filament 44 from whence the energization circuit is completed through a lead wire 78 on the opposite end of the filament 44 that electrically connects to a term inal 80 on'the insulated base 30 which is electrically connected by a conductor 82 to wire N. r

By virtue of the above-illustrated arrangement, when the control knob 18 is moved from an off position to a predetermined heat output setting, the filament 40 Will be energized pulsatingly to maintain a desired energy output corresponding to the knob setting under the control of the heater 64 and polymetallic element 66 which pulses the energy input to the resistance element 40. In order to obtain desirable heating effects by the surface heating unit 16 in the illustrated arrangement, the resistance wire 40 is constructed of tungsten and may have an energy output capability of 2500 watts depending upon the setting of the control knob 18. i

In the illustrated embodiment, the tungsten resistance element or filament 40 is responsive substantially instantaneously to being connected across the wires L L to self-heat into an extremely high temperature range between 4000 F. to 5000 F. at which temperature a substantial percentage of the energy input thereto is emitted as infrared radiaion which is passed either directly upwardly through the bulb 32 and the utensil supporting plate 18 for heating'utensils supported on the unit or is reflected from the infrared reflective surface 42 upwardly through the bulb 32 and the support plate 18. A substantial amount of visible light also is directed from the filament 40 to illuminate the plate 18. In order to obtain a controlled heat output, the filament 40 is pulsatingly energized by the controller '48 at varying rates depending on the knob and, as a result, the visible light emissions from the filament 40 pulse on and off at a frequency corresponding to the energy pulses from controller 48. These pulsing visible light emissions can be extremely distracting. This is especially the case when part of the planar extent of the upper plate 18 is uncovered.

In accordance with' certain of the principles of the present invention, the provision of the secondary low wattage resistance element or filament 44 eliminates this problem in the following manner. As soon as the surface heating unit 16 is turned on, the knob 18 will close the energization circuit for the lower filament 44 so as to continuously energize it during the on time of the surface unit 16. The continuously energized filament 44 will continuously emit visible light that either directly illuminates orilluminates the upper plate 18 by reflection from the surface 42 so as to pr duce a continuous background of illumination throughout the planar extent of the upper plate 18 that will damp out the pulsing light emissions from the higher wattage primary heating filament 40 during the operation of the unit 16.

The illustrated embodiment of th invention is merely one form of an infrared surface heating unit that can include a primary heating element that p l e i b light emissions therefrom and a secondary lower wattage continuously energized resistance wire for effectively masking the pulsating effect of the first resistance wire. The provision of such dual filaments for eliminating pulsing visible light in an infrared surface heating unit is equally applicable to a surface heating unit of the type wherein the resistance wires 'are unsealed and formed of high temperature electrical resistance material such as electrical resistance material from the nickel-chromium family or the iron-chromium-aluminum family that .is energizable in the range of 1500" F, to 2000 F. which temperatures also produce visible light emissions from the resistance elements. In this case, the resistance elements are able to operate in an unevacuated atmosphere as contrasted to the evacuated glass bulb environment of the illustrated embodiment. Furthermore, it will be appreciated that the filaments might be supported with respect to the infrared transmissiveupper utensil supporting plate in a fashion other than that illustrated. One example of another suitable manner of relating an infrared emissive high temperature resistance element to anupper plate ofinfrared transmissive material is fully disclosed in a copending application of an infrared surface unit, Ser. No. 429,305,

' filed Feb. 1, 1965, in the name of Donald C. Siegla. This application may be referred to for examples of infrared transmissive materials suitable for use in the plate 18 and bulb 32.

The words top, bottom, upper and the like are used merely for facilitating the description and are made with reference to the parts of a surface unit positioned as in FIGURES 1 and 2.

While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows: 1. An infrared surface heater unit for a range or the like comprising, an upper utensil supporting plate of infrared transmissive material, a support member located below said upper utensil supporting plate, said support member having an infrared reflective surface thereon underlying said upper utensil supporting plate, a first electrical resistance element disposed between said upper utensil supporting plate and said support member out of direct heat transfer contact with said upper plate and said support member, a second electrical resistance element disposed between said upper utensil supporting plate and said support member out of direct heat transfer contact with said support member and said upper plate, said second electrical resistance element having a wattage rating less than that of said first electrical resistance element, first energization circuit means including means for continuously'energizing said second electrical resistance element during operation of the heater unit to produce continuously visible light observable through said upper utensil supporting plate, second energization circuit means having switch means including energy pulsing means for pulsatingly connecting said first resistance element across a source of power for varying the energization thereof into and out of the visible light range, said continuously energized second resistance element serving to produce a background illumination of said upper utensil support plate for masking out the pulsing light-output of said first electrical resistance element during energy controlling operation by said second energization circuit means.

2. An infrared surface heater unit for a range or the like comprising, an upper utensil supporting plate of infrared transmissive material, a support member located below said upper utensil supporting plate, said support member having an infrared reflective surface thereon underlying said upper utensil supporting plate, a first electrical resistance element disposed between said upper utensil supporting plate and saidsupport member out of direct heat transfer contact with said upper plate and said support member, a second electrical resistance element disposed between said upper utensil supporting plate and said support member out of direct heat transfer contact with said support member and said upper plate, said second electrical resistance element having a wattage rating less than that of said first electrical resistance element, a first energization circuit including means for continuously energizing said second electrical resistance element during operation of the heater unit to produce a continuous vissible light source observable through said upper utensil supporting plate, a second energization circuit having switch means including energy pulsing means for pulsatingly connecting said first resistance element across a source of power for varying the energization thereof into and out of visible light range, said continuously energized second resistance element serving to produce a background illumination of said upper utensil support plate for masking out the pulsing light output of said first electrical resistance element during the energy controlling operation thereof by said second energization circuit means, said 6 first and second resistance elements being formed of tungsten, an evacuated enclosure, said resistance elements being located within said evacuated enclosure, said reflective surface being formed on an inner portion of said evacuated enclosure.

' References Cited UNITED STATES PATENTS 2,417,223 3/ 1947 Visitacion 219452 2,419,083 4/1947 Myers 219-449 2,804,531 8/1957 Dadson 219-452 2,859,368 11/1958 Biggs et al 219-552 3,132,229 5/1964 Bremer et al 219-448 RICHARD M, WOOD, Primary Examiner. L. H. BENDER, Assistant Examiner. 

